Feller-bunchers are typically used to fell or cut down trees from one site and then bunch the trees together to place them in a pile. Site prep tractors, on the other hand, are typically used to clear brush, tree stumps and other materials from a site. Both feller-bunchers and site prep tractors may be articulated machines that include a front frame and a rear frame that are pivotally coupled together by a hitch. The hitch allows the front frame to pivot relative to the rear frame for steering the feller-buncher or site prep tractor. Both the front and rear frames include an axle having a pair of wheels mounted thereon.
An engine mounted on the rear frame supplies mechanical power directly to a drop box via a hydrostatic transmission. The drop box splits the power output from the engine between the front axle and the rear axle. A portion of the power from the drop box is supplied directly to the rear axle via a drive line and the rest of the power is supplied to the front axle via a drive shaft and universal joint that passes from the rear frame to the front frame at the hitch.
The engine may also power a hydraulic system that supplies pressurized hydraulic fluid to several non-drive tool systems. Generally, wheel feller-bunchers may include a hydraulically powered rotating saw which is used to cut down the trees during a felling operation. In addition, a feller-buncher may have a number of hydraulically powered work arms which are used to secure the felled trees to the feller-buncher after the trees have been cut down. A site prep tractor may be provided with a number of hydraulically powered attachments such as a rotary axis mower, a side cut felling saw and/or a stump grinder. A number of hydraulically powered cylinders may be used to raise, lower, and tilt the tool systems.
One problem associated with current wheel feller-buncher and site prep tractor designs is the location and orientation of the engine and hydraulic system. Specifically, the engine is typically installed behind the cab and is directed longitudinally towards the cab and tool system. This design provides poor weight distribution across the rear axle and causes many operators to add weight to the rear of the machine to act as a counterbalance. Further, the excess weight of the counterbalance at the rear of the machine causes fuel and oil reserves to migrate towards the rear the machine, thereby possibly creating additional weight imbalance.
Another problem associated with current wheel feller-buncher and site prep tractor designs involves the location of the hydraulic system in the same compartment as the engine. The congested nature of the design does not permit adequate airflow for maximum cooling. Further, both the congested nature of the design makes it difficult to access the engine and the hydraulic system for servicing and maintenance.
Therefore, there is a need for improved wheel feller-buncher and site prep tractor designs that provide improved weight distribution, serviceability and cooling. For the sake of simplicity, wheel feller-bunchers and site prep tractors will be collectively referred herein to as “wheeled forestry tractors.”